The present invention is of an improved apparatus for performing in-situ machining and refacing of nuclear reactor feedwater inlet nozzles and the like and should find wide application, where suitable, for operation on similar devices where machining or refacing is necessary.
In general, nuclear reactor vessels are formed with a plurality of radial opening which radial openings are utilized to convey suitable liquid, such as water, to a vessel portion of the reactor wherein said liquid is utilized for shielding, conversion to steam, emergency flooding and for the extraction of generated steam from the vessel. The radial openings for feeding liquid to such vessel portion are formed with piping welded to said openings for conveying the liquid and steam to and from the vessel.
During construction of the vessel and at times after the vessel has been in use, it becomes necessary to machine or re-machine the radial openings within the reactor vessel. There are many constraints upon the manner in which such machining or re-machining may be carried out by reason of the nature of the reactor vessel.
One of the constraints requires that a rigid platform capable of supporting heavy weight and maintaining accurate positioning and alignment of machine and tools not be supported upon the interior platform of the vessel.
Another constraint requires that no welding of temporary support structures be made to the walls of the vessel.
A further constraint is found in a situation where the reactor vessel has been in use and the high levels of radiation permit very short duration work periods for people assigned to work within the vessel.
Other constraints will be well known to those practicing the art or be apparent from the discussions with respect to the drawings and the description of said drawing.
It is an object of the present invention to provide a new and improved boring and facing apparatus for machining or re-machining openings such as are found in nuclear reactor vessels and the like.
It is a further object of the invention to provide a new and improved boring and facing apparatus for machining or refacing openings which are radially disposed in a nuclear reactor vessel and wherein said apparatus may be readily and accurately positioned and remotely operated for accomplishing the desired operation.
It is a further object of the invention to provide a new and improved method for machining and refacing nuclear reactor feedwater inlet nozzles.
The objects of the invention are attained by the apparatus herein generally described. The apparatus is formed to be suspended from above the platform or floor end of the vessel, thus overcoming a major constraint upon the placement of a heavy weight upon the platform or floor of the vessel. To avoid weldments to the wall of the vessel during the period when the apparatus herein described is used for its intended purpose, use is made of existing sparger brackets to which the apparatus is coupled.
The apparatus is provided with a supportive structure which spans the upper opening of the reactor vessel resting on the upper wall and having a first plurality of wheels for rotation of the structure and a second plurality of wheels within the structure, perpendicular to the first plurality of wheels to keep the structure from running off the top of the reactor vessel. A plurality of jacks are provided proximate the first plurality of wheels so that the first plurality of wheels may be raised to prevent rotation of the supportive structure during use of the apparatus.
From the supportive structure a main frame or cradle is suspended by hanger rods. The main frame is provided with outriggers, the free end whereof are adapted to engage and be connected to the sparger brackets of the vessel. A first pair of vertical nose pads are provided at the front end of the main frame between the outriggers, are intended to abutt the vessel wall and provide part of a structure for connecting thrust of a boring machine which is mounted in the main frame. The other part of the structure for countering thrust of the boring machine comprises a spreader bar having one end coupled to the back end of the main frame and the other end coupled to a second vertical pair of nose pads which engage the vessel wall at a point substantially diametrically opposite the vessel wall engaged by the first pair of vertical nose pads.
The boring machine referred to above is mounted upon a set of ways for movement toward and from the front end of the cradle and the machine is provided with a chuck for mounting a tool desired to perform a boring and/or facing operation. A table may be interposed between the ways and the main frame to permit vertical or skew positioning of the boring machine relative to the cradle.
Other objects and advantages of the present invention as well as a more detailed description of the invention will be obvious to those skilled in the art when reference is had to the specification and drawings herein.